US2942221A - Sub-miniature concentric tandem variable resistor and switch control - Google Patents

Description

June 21, 1960 J. DI GIROLAMO 2,942,221

SUB-MINIATURE CONCENTRIC TANDEM VARIABLE RESISTOR AND SWITCH CONTROL Filed July 11, 1957 4 Sheets-Sheet 1 mm 27 e3 20 47 LVARIABLE LMULTI-POSITION '1 RESISTOR SWITCH ON-OFF June 21, 1960 J, DI GIROLAMO 2,942,221 SUB-MINIATURE CONCENTRIC TANDEM VARIABLE RESISTOR AND SWITCH CONTROL 4 Sheets-Sheet 2 Filed July 11, 1957 June 21, 1960 J. DI GIROLAMO 2,942,221

SUB-MINIATURE CONCENTRIC TANDEM VARIABLE RESISTOR AND SWITCH CONTROL Filed July 11, 1957 4 Sheets-Sheet s Jcsaph .Uwmlamc;

June 21, 1960 J. DI GIROLAMO 2,942,221

SUB-MINIATURE CONCENTRIC TANDEM VARIABLE RESISTOR AND SWITCH CONTROL Filed July 11, 1957 4 Sheets-Sheet 4 H 27 J59 hIhQzraZama sg ai g hgw United S ttes Patent SUB-MINIATURE CONCENTRIC TANDEM VARI- ABLE RESISTOR AND SWITCH CONTROL Joseph Di Girolamo, Mishawaka, Ind., assignor to CTS Corporation, Elkhart, Ind., a corporation of Indiana Filed July 11, 1957, Ser. No. 671,356

8 Claims. (Cl. 338-200) sufiicient size reduction in such concentric tandem controls, as to permit their use in the so-called transistoriz ed radio receiving sets wherein transistors are used in place of the more conventional tubes, and especially in transistorized automotive sets where ruggedness is a primary consideration. Y

The extent to which this invention has attained its objective can be readily appreciated from the fact that in one embodiment thereof comprising a four-position tone control switch, a variable resistor and an on-olf switch, the overall size of the control is only nine sixteenths of an inch in diameter and three-fourths of an inch in length.

Prior concentric tandem controls did not lend themselves to such miniaturization because mere proportional reduction in the size of the component parts thereof was limited by the need for maintaining adaquate electrical clearance between grounded and live parts. Also, there is a limit to the extent shaft diameters may be reduced in a concentric tandem control, especially in automotive sets where ruggedness is required.

The crux of the problem resided in the fact that, with prior constructions, the center connector of the variable resistor and, more particularly, the manner in which it was constructed and orientated with respect to the resistance element, positively limited the size reduction which could be' effected. Accordingly, if the end sought by this invention was to be reached, an entirely new form of center connector would have to be devised. This has been done.

Another facet of this invention resides in the fact that j the individual units of the complete control are'so constructed as to achieve an unprecedented flexiblity in assembly. Thus, with this invention, it is a simple matter to assemble into one combination control, two

individual variable resistors and an on-off switch; a multi- 4:

appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by. the appended claims, it beingunderstood that such changes in the precise embodirnent of the hereindisclosed invention may be made as come within the scope of the claims.

; .'The accompanying drawings illustrate one complet example of' the physical embodiment of this invention ponstructed according to the best mode so far devised Patented JuneZl, 1960 ice for the practical application of the principles thereof, and in which:

Figure 1 is a perspective view of a concentric tandem control embodying this invention, viewing the same essentially from the front;

Figure 2 is a longitudinal sectional view through the control shown in Figure l, and which, as is here clearly shown, comprises a multi-position switch, a variable resistor and an on-ofif switch;

Figure 3 is a perspective view of the control, viewing the same from the rear but with the base of the on-off switch, which also serves as the rear wall of the unit, removed and swung around to display the inside aspect thereof;

Figure 4 is a perspective view showing the rear of the fore part of the control, with the variable resistor parts pulled off and swung around to show the front thereof;

Figure 5 is an exploded perspective view of the multi position or tone control switch viewing some of the parts thereof from the rear and the remainder thereof from the front;

Figure 6 is a perspective view of one of the component parts of the multi-position switch shown separated from the rest of the structure;

Figure 7 is a perspective view of the center connector or collector ring of the variable resistor, shown separated from the rest of the structure;

Figure 8 is a perspective view of the stop washer which holds the coaxial shafts against relative endwise displacement and also provides a stop to limit rearward endwise movement of the rotors of the variable resistor and multiposition switch; and

Figure 9 is a longitudinal sectional view similar to Figure 2 but illustrating the composite control as com prising two variable resistors and the on-off switch.

Referring particularly to the accompanying drawings and especially to Figure 2, it will be seen that the complete control of this invention is contained within a housing structure built up of complementary parts, some of which are interchangable so as to give the control a desirable flexibility in assembly. This housing structure consists of two similar tubular side wall forming members 10 and 11, each formed of insulating material, and both having the same inside and outside diameters and length. Between the adjacent ends of these two tubular members is a partition wall 12 consisting of a disc of insulating material of a diameter slightly larger than that of the side wall forming members; and closing the front and rear ends of the housing structure are'end walls 13 and 14 each also formed by discs of insulating material slightly larger in diameter than the tubular members.

These five parts, together with a spacing washer 15 overlying the front wall 13 are held coaxially assembled by being confined between a metal ground plate v16 which bears against the washer 15 and inturned fingers 17 on the extremities of arms 18 extending rearwardly from the edge of the ground plate.

The arms 18 are received in aligned grooves 19 in th tubular side wall forming members and recesses 20 in the partition wall 12, the end walls 13 and 14 and the spacer 15, so that the arms 13 not only serve to hold the complementary housing parts in coaxial relationship, but also secure the same against relative rotation.

The ground plate 16 may have any suitable means provided thereon for mounting the control upon a panel, as for instance, the three forwardly projecting ears 21 which have panel engaging shoulders 22 and narrow tangs 23 projecting therefrom, to enter appropriately located holes in'the mounting panel (not shown), where :they are secured by being twisted or bent over or by the solder dip fastening method.

ass-2,22 1

The partition wall 12 divides the interior of the housing structure into axially adjacent front and rear compartments, each of which is adapted to contain at least one of the. individual units of the control. In that embodiment of the invention illustrated in Figure 2, the front compartment contains a multi-position or tone control switch, indicated generally by the numeral 24, and the rear compartment contains both a variable resistor, indicated generally by the numeral 25, and an on-off switch 26. This combination of control units can be easily altered due to the unusual interchangability of parts which this invention provides, and to illustrate th-ispoint, in the control shown in Figure 9 the multi-position tone control switch is supplanted by another variable resistor.

A characteristic of, this invention is that in the variable resistor as well as the multi-position switch, the front Wall of the compartment in which the control unit is located provides the base for the stator portion of the unit. Thus, in. the control shown in Figure 2, the pantition wall 12 has; the arcuate resistance element 27 fixed to the rear face thereof, and the front end wall 13 of the multi-position switchhas the stationary contacts 28, 29, 3t and 31, and the common contact 32 fixed on the rear face thereof. In the control shown in Figure 9, wherein the panel section or. unit of the control as well as the rear unit is a v aniableresistor, the. front endwall 13', like the partition wall, has an arcuate resistance element fixed thereon.

The; terminals 27' of the resistance element extend from theextremities thereof radially outwardly through notches 33 in the front end of the tubular side wall forming member 111,, and, the terminals 28', 29', 30,, 31 and 32' ofthe, stationary switch contacts similarly project radially out. through notches 34 in the front end of the tubular side wall: forming member 10. The notches 33 and 34 are just deep enough and wide enough to accommodate the terminalsareceived.therein and, accordingly, the terminals will. be firmly held against any possible displacement.

The heads of the rivets by which the terminals 27' are secured to the insulated base provided by the partition 12 (or the. front wall 13 when two resistors are mounted in tandem, as in Figure 9) with the ends of the resistance element 27 confined therebetween, project forwardly beyondv the front of the base. By the same token, the heads of the rivets by which the contacts 2341 and the ends of the tangs by which the common contact 32 are secured to the switch base, i.e. the front wall 13, project forwardly of this base. in the case of the partition wall 12 such forward projection of the rivet heads presents nov problem since, in this case, they merely extend into the front compartment but, in the case of the front or panel unit, whether it be a variable resistor or multiposition switch, the forwardly projecting rivet heads must 'beaccommodated and held from contact with the ground plate. 16. This is the function of the spacing washer 15 which is large enough to encircle and clear the adjacent forwardly projecting rivet heads and thick enough to adequately space them from the ground plate.

As is conventional in concentric tandem controls, the rotor of the front or panel unit is mounted on and driven by a tubular shaft 35, and the rotor of the rear unit is mounted on and driven by a shaft 36 which passes through and is journalled in the tubular shaft. Preferably, the shaft 36 is solid and especially so in the present instance where the utmost size reduction is being sought. These coaxial shafts are rotatably supported by having the outer tubular shaft journalled in aligned holes 37 and 38, respectively, in the front end wall 13 and the ground plate 16, and by having the rear end portion of thesolid inner shaft journalled' in a hole 39 in the rear end-wall 14. The partition wall 12 has a central aperture 40 through which the inner shaft projects.

The rotor of the multi-position switch comprises a circular drive, arm 41 molded of insulating material and having-a. forwardly. projecting hub 42 and an eccentrioally disposed rearwardly projecting-stop lug 43. This molded drive arm is fixed to the rear end of the tubular shaft by means including tangs 44 extending from the shaft and clinched over the rear face of the arm. A contactor 45 in the form of a ring stamped from suitable resilient metal is fixed on the front face of the circular drive arm in a position encircling the hub 42. The securement is effected by tangs 46 extending from diametrically opposite portions of the contactor and clinched around opposite notched portions of the drive arm. The unsecured portions of the contactor 45 are sprung forwardly and provided with diametrically opposite fingers 47 and 48, the former being adapted for'selective engagement with any one of the stationary contacts 28 to 31, and the latter riding upon the common contact 32.

Detent action to hold the switch rotor in any one of its four positions is provided by the engagement of the contact finger 48 into properly located holes 48 in the common contact.

The spring tension with which the contactor 45- engages the stationary switch contacts imposes a rearward axial thrust upon the tubular shaft 35. This thrust is resisted and limited by the engagement of a C-shaped stop washer 49 having its bight portion received in a slot 50 in the tubular shaft and bearing against thefront face of the ground plate. The bight of the C-shaped stop washer 49 also projects into an annular groove 51 in the solid inner shaft 36 and thereby holds the shafts against relative endwise displacement and also resists and limits rearward axial displacement of the inner solid shaft.

The rotor of the variable resistor, like that of the multiposition switch, comprises a molded circular drive arm 52 non-rotatably secured to the solidinner shaft 36 and provided with a forwardly projecting annular bead 53 and a rearwardly projecting eccentrically located stop 1ug'54. Fixed to and overlying the front of this molded drive arm and encircling its forwardly projecting head 53, is; a ringlike contactor 55 stamped of suitable resilient metal.

The contractor 55 has a fiat arcuate body portion. 56 with diametrically opposite. tangs 57 extended from the opposite'outer edges thereof and clinched over opposite notched portions of the drive arm to secure the contactor thereto with its body portion lying flat against the front of the drive arm. Arcuate spring contact fingers 58. ex.- tend from the ends of they arcuate flat body portion 56 to overlie the drive arm. These spring contact fingers are substantially coplanar with. the body portion and are axially'biased forwardly towards the resistance. element 27.v Their extremities are smoothly rounded and bear against the adjacent contact surface of the resistance element with. a force dependent upon the stiffness of the spring fingers. The rearward thrust imposed upon the rotor as a result of this spring contact pressure is resisted and limited by the stop washer 49, as explained hereinbefore.

Although the spring tension of the fingers 5 8 resists forward displacement of the rotor assembly of the vari able resistor, it is desirable to provide a positive limit to the extent this spring tension may be increased by an accidental or unintentional pull on the shaft, and for this purpose, the annular bead 53 has a height such that in the normal axial position of the rotor its edge is spaced just a short distance from the base (partition wall 12).

In the same manner, the hub 42 positively limits forward displacement of the rotor of the multi-position switch.

Bent back from its edge opposite that from which the contact fingers 58 project and at points close to but be.-. tween the tangs 57, the contactor has a pair of rearwardly directed parts 60 disposed at right angles to the body portion 56. These parts 60 have spring contact fingers 61 extended therefrom toward one another and overlying the periphery of the circular drive arm. The fingers 61 thus have widely spaced anchored, ends provided by the parts 60, and closely spaced outwardly biased free ends, theextremities of which are formed as smoothly rounded contacts 61 to engage the inside of a collector ring 62.

The collector ring 62 difiers materially from the collector rings ordinarily used in variable resistors employed in radio and television receivers, and because of this difference and the manner in which the spring fingers 61 of the contactor are arranged on the contactor to traverse the collector ring, an entirely unprecedented size reduction in controls of this type has been made possible.

As best seen in Figure 7, the collector ring 62 is a sheet metal stamping rolled up into a ring of a size to be snugly received in a counterbore 63 in the tubular member 11. It is held therein with its front edge bearing against the shoulder provided by the bottom of the counterbore, by a pair of diametrically opposite hold-down fingers 64 extending rearwardly from the ring and bearing against the rear end wall 14. A terminal 65 projects radially out from the rear edge of the ring 62 through a notch 66 in the wall of the tubular member and, in so doing, secures the ring against turning in the counterbore.

Since the ring is held against turning, it may be used to carry the stationary one of the cooperating stops by which the limits of rotary adjustment of the variable resistor are defined. To this end, the ring has a radially inwardly directed tongue 67 extended therefrom into the path of the stop lug 54.

Attention is directed to the fact that the bottom of the counterbore 63 which defines the position of the ring 62 in the tubular member, is located about medially between the ends of the member 10. This assures substantial electrical clearance between the resistance element and the collector ring.

The multi-position switch also has a stamped and rolled-up metal ring 70 which .is quite similar to the ring 62, seated in a counterbore 63' in the tubular member 10 and confined between the bottom of the counterbore and the partition wall 12 by diametrically opposite hold-down fingers 71 extended from the rear edge of the ring. However, in this case, the ring has no electrical function and serves only to limit rotation of the switch rotor. For this purpose, the ring 70 has a pair of inwardly directed stop lugs 72 formed thereon to lie in the path of the stop abutment 43 on the switch rotor, and an out-turned lug 73 which is received in a notch 74 in the wall of the tubular member 10 to hold the ring 70 against turning.

The on-off switch 26, which as indicated hereinbefore is contained Within the rear compartment along with the variable resistor, comprises a stationary contact 75 fixed to and projecting forwardly from the rear end wall 14 and a resilient switch blade 76 anchored as at 77 to the end wall 14 and biased into engagement with the stationary contact, as clearly shown in Figure 3. The terminals 78 and 79 for the switch comprise a rearward extension of the stationary contact 75 and a similar extension on the rivet 80 by which the blade 76 is anchored.

A cam 81 non-rotatably mounted upon the rear end of the solid shaft 36 engages the switch blade to disen gage it from the stationary contact upon adjustment of the variable resistor rotor to one limit of its permitted rotation.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention has achieved an entirely unprecedented reduction in the overall size of concentric tandem variable resistor-switch controls, and that the key to this achievement resides in the novel reorganization of the parts of the variable resistor and, more especially, in the manner in which the collector ring is disposed with respect to the rotor of the variable resistor.

It will also be apparent that this invention has attained a new versatility in the combination of elements making up such concentric tandem controls, since the housing sections are substantially the same for the variable resistor and the multi-position switch.

What is claimed asmy invention is: l. A concentric tandem radio and television control of the type wherein a plurality of control units are disa posed in concentric tandem relation and have rotors discs of-insulating material; a partition wall provided by a similar disc of insulating material, entirely separate from the side wall forming members, and clamped between the adjacent ends of the tubular members to di vide the housing structure into axially adjacent front and rear compartments, eachof which contains one of the control units; a metal ground plate overlying the disc forming the front end wall of the housing structure; arms integral with the ground plate extending rearwardly over the tubular members and said discs; and fingers on the extremities of said arms clinched over the disc which provides the rear end wall to thus hold the tubular members and said discs assembled and in coaxial relationship; the shafts passing through aligned holes in the disc which provides the front end wall and in the ground plate, the outer shaft terminating inside the front compartment to drive the rotor of the control unit therein and the inner shaft projecting beyond theouter shaft and through a hole in the partition wall into the rear compartment to drive the rotor of the control unit therein.

2. The structure of claim 1 further characterized by the fact that the rotor of each of the control units has a rotation limiting stop abutment thereon to collide with a stationary stop abutment to define the limits of rotation of the rotor, and characterized further by the fact that each stationary stop abutment comprises a finger directed inwardly from a metal ring inserted into each tubular member from the rear end thereof and held against endwise displacement from a position at which said finger lies in the path of the stop abutment on the rotor, by being confined between a shoulder on the wall of the tubular member and the disc at the rear end thereof, the ring being secured against turning by a finger projecting radially out from the ring and engaging in a recess in the tubular member.

3. The structure of claim 2 further characterized by the fact that each tubular member is counterbored from its rear end, and by the fact that the ring is seated in the counterbore with its front edge bearing against the bottom thereof so that the bottom of the counterbore provides said shoulder on the wall of the tubular member.

4. The structure of claim 2 further characterized by the fact that one of said controls is a variable resistor comprising an arcuate resistance element having a fiat contact surface and a rotatable contactor having a spring contact finger to traverse said surface of the resistance element and another spring contact finger to traverse a collector ring; the arcuate resistance element being mounted on the disc comprising the front of the housing compartment in which the variable resistor is located; and the contact finger which traverses the collector ring being biased radially outward into engagement with the inner surface of said metal ring so that said metal ring serves as the collector ring of the variable resistor as well as a carrier for the stationary stop abutment.

5. The structure of claim 1 further characterized by the fact that the disc closing the rear end of the housing structure has cooperating stationary and movable switch contacts mounted on its inner face; and means to con trol engagement between said contacts formed on the rear end of the inner shaft which drives the rotor of the control in the rear compartment.

6. As an article of manufacture, a contactor for the rotor of a variable, resistor comprising: a unitary sheet metal stamping having a flat body section; a pair of mounting ears at substantially opposite side edges of the flat body section extending in the same direction perpendicularly to the plane of said section; a pair of resilient generally fiat contactor fingers extending from an edge of the body section at points near the mounting ears with said fingers projecting in the same general direction from and substantially coplanar with the fiat body section, said contact fingers being resiliently yieldable in a direction normal to the plane of the fiat body section and being biased in the same direction out of said plane; and a second pair of resilient contact fingers each having an anchored end portion provided by at part of the stamping which; is bent at right angles from an edge portion of itsfiat body section, said second pair of contact fingers extending from their respective anchored ends toward each other and having their free ends near one another, and said second pair of contact fingers being resiliently yieldable in directions parallel to the plane of the flat body section.

7. In a control of the character described: a housing for the instrumentalities of the control including a cylindrical side wall of insulating material, said side wall being; counterbored from one end thereof and having a notch extending axially in from said end and opening to the counterbore; a metal ring seated in the counteubore with one edge thereof bearing. against the bottom of the counter-bore and its other edge spaced inwardly of the open end of. the counterbore; an end wall across said end of the cylindrical side wall; a part on the metal ring extending axially from its said other edge and engaged by the end wall so that the end wall holds the metal ring down against the bottom of the counterbore;v a lug projecting radially outwardly from said ring into said notch to thereby hold the ring against turning with respect to the side wall; a stop lug on the ring projecting radially inwardly thereof; a rotor constrained to rotation about an axis coaxial with the cylindrical side wall with a part thereof inside said cylindrical side Wall; and stop means on the rotor engageable with said stop lug to define the limits of rotation of the rotor.

8. The structure of claim 7 wherein said control is a variable resistor and wherein said metal ring provides an. annular collector contact for the resistor, and said radially outwardly projecting lug provides a terminal for said contact, and further characterized by the provision of a resilient contact finger on the rotor resiliently hearing against the inner surface of said metal ring.

References Cited in the file of this patent UNITED STATES PATENTS 1,572,645 Francesco Feb. 9, 1926 1,779,601 Kebler Oct. 28, 1930 2,506,491 De Boisblanc May 2, 1950 2,572,651 Mucher Oct. 23, 1951 2,712,583 Mucher July 5, 1955 2,789,191 Arisman et al Apr. 16, 1957

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